Another consideration is it all depends upon where you're located--geographically, company-wise, and technology area. At least in my observation.
Infrastructure tends to have less ageism than development/software engineering. Large corporations relatively less than start-ups (agism in corps is usually tied to/masked by salary level; "it's about cutting costs"). Midwest/rural areas less than large metros and "hip locations" (due mainly to smaller pools of potential employees).
"Midwest/rural areas less than large metros and "hip locations" (due mainly to smaller pools of potential employees)."
Unfortunately that has not been my experience at all. Aside from personal experience, I read constantly on HN about how you can walk in off the street and get a job in SV and NYC if you have any skills at all.
To say that's not the experience here would be an understatement. You pretty much have to know someone. One advantage of being in this game since '81 is I know a lot of people. A BSCS from a decent school will get you a job in midwest/rural, its just going to be entry level helpdesk resetting email passwords, or pulling cat5 cable. Probably about half of grads are underemployed, I see them at work all the time.
Not to say there's no advantages; if you can get one of the "good jobs" the standard of living is spectacular in midwest/rural compared to the coasts, and there's better recreation (well, depends on your personal likes/dislikes, etc). Culture is better, generally.
Every once in a while, I take a 90 minute, 100 MPH commuter train into downtown Chicago and remind myself why I don't want to live in a big city. Or go to a conference on the coasts, or visit Europe again. I don't live in a big city; that's why I can easily afford that kind of lifestyle.
Infrastructure tends to have less ageism than development/software engineering. Large corporations relatively less than start-ups (agism in corps is usually tied to/masked by salary level; "it's about cutting costs"). Midwest/rural areas less than large metros and "hip locations" (due mainly to smaller pools of potential employees).